v0.2.0 — Local resume

Untracked containers now remember where you left off in a video. Because
yt-untrack blocks YouTube's watch-tracking pings, YouTube can no longer save
your resume position server-side, so partially-watched videos used to restart
at 0:00. This version restores that: the last playback position is stored
locally (per container, per video) and the player silently seeks back to it
when you reopen the video — just like native resume, but without touching your
account history.

• Active only in untracked containers; normal containers are unchanged.
• Finished videos start fresh; explicit ?t= links are respected.
• Positions are kept locally in the extension only, never transmitted, and are
  pruned after 90 days.